


saccharine

by Alunala



Series: med school au [2]
Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - College/University, Alternate Universe - Medical, Blue Lions Students-centric (Fire Emblem), Dialogue Heavy, Gen, no beta we die like Glenn
Language: English
Status: Completed
Published: 2021-02-10
Updated: 2021-02-10
Packaged: 2021-03-16 18:28:24
Rating: Not Rated
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,827
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29336805
Author URL: https://archiveofourown.org/users/Alunala/pseuds/Alunala
Summary: The Blue Lions attempt to study for an exam. Chaos ensues.
Relationships: Felix Hugo Fraldarius/Sylvain Jose Gautier
Series: med school au [2]
Series URL: https://archiveofourown.org/series/2130021
Kudos: 8





	saccharine

“Annie, do you remember how the parasympathetic nervous system affects the eye?” Mercedes asked. Their class had an anatomy and physiology midterm the next day, so all of the Blue Lions were studying for their midterm like crazy.

Annette rested her head on her left arm as she quickly jotted something down in her notebook, “Acetylcholine latches onto the muscarinic receptors on the smooth muscle of the eye and causes it to constrict, leading to less light entering the retina. It’s excitatory because it actively causes the pupil to constrict, rather than preventing the pupil from opening.”

Mercedes nodded as she looked at her notes, “Good job Annie, that’s exactly what I had written down! Now Dedue, can you tell me what the sympathetic nervous system does to the eye?”

The darker-skinned man nodded as he thought for a few seconds, “I know that it’s excitatory which means that it wants to create an action potential.”

He paused for a few seconds before continuing, “Norepinephrine latches onto the  α 1 receptors of the radial smooth muscle, causing dilation of the pupils. Since it uses Norepinephrine, it’s considered to be adrenergic.”

“I believe that’s right,” the gray haired man that was sitting next to him said, “The pupils dilate in response to low light levels to allow more light to be entered into the retina.”

Sylvain drew himself closer to his boyfriend, Felix to the point where the two were practically intertwined, “Hey, I just saw your pupils dilate! That means I just stimulated your sympathetic nervous system by causing norepinephrine to latch onto the  **α** 1 receptors of your eyes.”

“You are so annoying,” Felix said, rolling his eyes, “Boar. How does the parasympathetic nervous system affect the bronchioles?”

Dimitri flipped to a page in his notes and began to answer until Felix stopped him, “Preferably without the notes. You remember Professor Hanneman’s policy of cheating, don’t you?”

Dimitri showed Felix the page he was looking at, revealing that it was just a blank piece of paper, “The bronchioles are smooth muscle, meaning that they have muscarinic receptors that acetylcholine will bind to. In the bronchioles, acetylcholine has an excitatory effect. The bronchioles constrict in response to relaxation in order to minimize the surface area that blood has to be pumped through in order to be oxygenated.”

“Wow Dimitri, that was a really good answer,” Ingrid said, “Do you mind if I answer how the sympathetic nervous system impacts the bronchioles? I’m really uncertain of my answer.”

“No, not at all, Ingrid,” Dimitri replied, flipping to the page where the sympathetic nervous system was in his notes, “If you need any help, I can help you along.”

Ingrid nodded, “Well I know that the sympathetic nervous system causes the bronchioles to open, which is in response to norepinephrine binding onto  β2 receptors. This occurs when the body needs to take in more oxygen.”

“That’s correct Ingrid, now can you remember whether it’s inhibitory or excitatory?”

Ingrid shook her head, “Shit, no, I can’t.”

“Well in my notes here, it says that it is inhibitory. I think the textbook said that as well.”

Ingrid began to write that down in her notes, “Thank you so much.”

“Anyways, does anyone want to tell me how the parasympathetic nervous system affects the gastrointestinal tract,” Mercedes said, checking a checklist that she had written a variety of information on.

Ashe’s face lit up, “I think I know it. Do you mind if I answer?”

Mercedes nodded, “Go ahead.”

“Well the Gastrointestinal tract, otherwise known as the GI tract is made up of smooth muscle. It has muscarinic receptors that acetylcholine binds to, causing it to contract, otherwise known as peristalsis. This mechanism helps it churn food and move it further along the GI tract. It has an excitatory effect,” Ashe said, looking at the ceiling as if it would help him remember more about the parasympathetic nervous system.

“That’s very good Ashe. Sylvain, can you tell us how the sympathetic nervous system affects the GI tract?”

“Damn Mercedes,” Sylvain complained, “this is the one thing I didn’t study.”

Felix rolled his eyes at Sylvain, “Well, you never study and somehow your grades are better than mine. Answer the question.”

“Man, I barely know this one. All I know is that there are  α 1 receptors on the smooth muscle on the GI sphincters that allow norepinephrine to bind onto it which causes the sphincters throughout the gastrointestinal tract to close because they contract. This is an excitatory effect because the GI tract is actively receiving action potentials that cause the sphincters to stay closed,” Sylvain said, before continuing.

“Furthermore, the sympathetic nervous system also affects the smooth muscle of the GI tract, not just sphincters. This time, norepinephrine binds onto the  β2 which causes the muscle to relax, slowing the movement of food, which means that it prevents digestion from occurring. I guess you can remember this because if you put two beta signs together, it looks like a butterfly and when you get nervous, it feels like you have butterflies in your stomach. And if it isn’t obvious enough, the sympathetic nervous system takes charge in times of stress.”

Felix stared at Sylvain with his amber eyes, “And you say you don’t study much.”

“Hey, it’s true,” Sylvain said, telling the truth, “This stuff just kind of clicks in my brain for some reason.”

“Regardless of whether you’ve studied or not, that was a really good answer,” Mercedes said, “I’ll definitely be writing it down. Does that mean that the sympathetic nervous system has an antagonistic effect on the smooth muscle of the GI tract?”

Sylvain nodded, “Yes, because the two systems have an opposite effect on the smooth muscle, you could say that they are antagonistic muscles.”

A girl with white hair joined their table and sighed, “Ugh, Lorenz is annoying me. I figured I’d join you guys because you seem like you’re actually studying and not just goofing around.”

“I don’t mind if you join Lysithea,” Felix said, looking over to the ‘Golden Deer’ table where they didn’t seem to be getting much work down. It appeared that the purple haired man, Lorenz, was getting into an argument with the green-eyed man named Claude. 

Lysithea sighed in relief, “I am grateful. Those two were getting on my nerves. Aren’t they concerned that they have a midterm tomorrow?”

“Apparently not,” Sylvain said, “Lysithea, you’re really smart. Can you tell us how the parasympathetic nervous system works on the heart.”

Her pink eyes shined with knowledge, “Of course! I know how it works. The parasympathetic nervous system has an inhibitory effect on the cardiac muscle of the heart. Acetylcholine binds onto the muscarinic receptors of the heart and as a result, it slows down the action potentials of the heart, causing the heart to relax more in between contractions. The parasympathetic nervous system impacts the pacemaker potential of the heart and alters the ‘slope’ of the action potential by decreasing the speed that calcium enters the cell. If you remember how Hanneman emphasized that the pacemaker potential is different from any regular action potential, you’d remember that instead of hyperpolarization (which is caused by sodium leaving the cell) occurring, the cell immediately starts depolarizing again, caused by the sodium and calcium channels slowly opening until the the threshold is reached, causing the cell to start depolarizing again. The parasympathetic nervous system essentially makes it take longer to reach threshold, effectively slowing the heart rate. Since the vagus nerve only reaches the sinoatrial and the atrioventricular nodes, it doesn’t have an impact on the strength of heart contractions.”

“Wow,” Annette said, “You’re so much smarter than I am!”

“Nonsense,” Lysithea disagreed, “Your answers to Hanneman’s questions are always very eloquent and put-together.”

“Both of you guys are very smart!” Mercedes said, “Annie, why don’t you answer how the sympathetic nervous system impacts the heart.”

Annette nodded, “Of course! Norepinephrine binds onto the β1 receptors of the heart and it is an excitatory effect. It actively increases the frequency of the heart’s contractions and it also increases the strength of contractions. Hanneman talked about sliding filament theory here and how actin and myosin require calcium in order to shorten the muscle, causing it to contract and that more calcium causes stronger contractions.”

“That’s correct Annie!” Mercedes said, “Good job. Now, I’ll share my answer for the parasympathetic nervous system’s effect on the bladder and Felix can share his for the sympathetic nervous system!”

Felix sighed, “Whatever.”

“The bladder, like all the other smooth muscles that is impacted by the sympathetic nervous system, has muscarinic receptors that acetylcholine binds onto. The excitatory effect that the sympathetic nervous system has on the bladder causes it to contract in order to rid it of urine. The inhibitory effect is the sphincter of the bladder being opened and causing urine to leave the bladder.” 

“That sounds right,” Dimitri said, “Felix, what effect does the sympathetic nervous system have on the bladder?”

“Well the sphincter of the bladder is made up of smooth muscle and on that smooth muscle, there are α1 receptors norepinephrine binds to, causing an excitatory effect on the sphincter. This means that the sphincter of the bladder is actively being kept shut by the sympathetic nervous system,” Felix grumbled absentmindedly.

Mercedes gave Felix a short smile, “That was a really good answer! Good job Felix! Dedue, can you answer how the sympathetic nervous system impacts the blood vessels?”

Before Dedue had a chance to answer, Lorenz tapped Lysithea on the shoulder, shocking the girl so badly that she let out a tiny shriek, “What do you want Lorenz?”

“Can you tell Claude to give me back my phone? He took it and now he’s Snapchatting all of my friends,” Lorenz complained, tucking his purple hair behind his ear.

Lysithea shook her head, “Can’t you  _ see  _ that I’m trying to study? Go away!”

“Well when Claude takes my phone, it causes my sympathetic nervous system to activate, causing norepinephrine to bind to the  α1  receptors in my blood vessels, causing them to constrict which in turn, raises my blood pressure. The only way to stop my sympathetic nervous system from keeping my blood vessels constricted is to talk to Claude and tell him to give me back my phone.”

Dedue did not say anything to Lorenz despite the fact that the purple-haired man had answered the question that he had answered. 

“I think that’s a sign that we’ve been studying for too long,” Felix said. Ever since Lysithea had shown up at the table, he had found himself unable to focus on his studying. It wasn’t for any reason, it was just because his attention span was limited and the smallest thing could break his focus.

Mercedes nodded, “I’ll help Lorenz get his phone back. If anyone wants to meet up tomorrow, let me know in the group chat and I can arrange something!”

  
  
  
  
  
  
  
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**Author's Note:**

> Thank you so much for reading! As always I love comments!


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